Wireless communication system and connection method between user equipment and a mobility management entity

ABSTRACT

The present invention relates to a wireless communication system and a connection method between user equipment and a mobility management entity and comprises: selecting a mobility management entity and requesting identification information for user equipment by a base station when the user equipment is connected; determining whether to assign identification information by the mobility management entity; and if the identification information is not assigned, selecting another mobility management entity by the mobility management entity, assigning identification information to the user equipment by the other mobility management entity, and performing a connection with the other mobility management entity by the user equipment. According to the present invention, user equipment can be efficiently connected with a mobility management entity in a wireless communication system.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 13/577,750, filed on Aug. 8, 2012, which is a U.S. NationalStage application under 35 U.S.C. §371 of an International applicationfiled on Feb. 9, 2011 and assigned application number PCT/KR2011/000866,which claimed the benefit of a Korean patent application filed on Feb.10, 2010 in the Korean Intellectual Property Office and assigned Serialnumber 10-2010-0012548, the entire disclosure of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system andmethod and, in particular, to a wireless communication system and amethod for establishing a connection between a user equipment and amobility management entity.

2. Description of the Related Art

Universal Mobile Telecommunications System (UMTS) is a third generationwireless communication system based on the Global System for Mobilecommunication (GSM) and General Packet Radio Services (GPRS) and usingWideband Code Division Multiple Access (WCDMA). The 3rd GenerationPartnership Project (3GPP) for UMTS has proposed Evolved Packet System(EPS) such as Long Term Evolution (LTE). LTE is a technology for highspeed packet-based communication network. An LTE mobile communicationsystem is provided with a Mobility Management Entity (MME) which isconnected to the User Equipment (UE) and responsible for managingmobility of the UE.

SUMMARY

With the diversification of the communication services provided by thewireless communication system, the UE is also equipped with varioussupplementary functions. The MME is configured to support thesupplementary functions of the UE. In order to use the communicationservice associated with a supplementary function, the UE has to connectto the MME supporting the supplementary function. There is therefore aneed of a method for a UE to connect the MME supporting thecorresponding supplementary function efficiently.

In accordance with an aspect of the present invention, a method forconnection between a user equipment and a mobility management entity ina wireless communication system includes requesting, at a base stationwhen a user equipment is connected, identity information for the userequipment to a mobility management entity; determining, at the mobilitymanagement entity, whether to allocate the identity information to theuser equipment; requesting, when determined not to allocate the identityinformation, another mobility entity for the identity information;allocating, at the other mobility entity, the identity information tothe user equipment; and attempting, at the user equipment, connection tothe other mobility management entity with the identity information.

Preferably, determining includes judging whether the mobility managemententity has a function supporting the user equipment; determining, whenthe mobility management entity has the function supporting the userequipment, allocation of the identity information; and determining, whenthe mobility management entity has no function supporting the userequipment, no allocation of the identity information.

Preferably, determining includes judging whether a load of the mobilitymanagement entity is greater than a predetermined threshold value;determining, when the load is greater than the threshold value, notallocation of the identity information; and determining, when the loadis not greater than the threshold value, allocation of the identityinformation.

In accordance with another aspect of the present invention, a wirelesscommunication system includes a user equipment having identityinformation; a mobility management entity which allocates the identityinformation to the user equipment, establishes a connection with theuser equipment using the identity information, and manages mobility ofthe user equipment; and a base station which selects, when the userequipment is connected, the mobility management entity to request forthe identity information, wherein the mobility management entitydetermines, when the base station request for the identity information,whether to allocate the identity information to the user equipment andrequests, when determined not to allocate the identity information,another mobility entity for the identity information.

Preferably, the mobility management entity judges whether the mobilitymanagement entity has a function supporting the user equipment,determining, when the mobility management entity has the functionsupporting the user equipment, allocation of the identity informationand, otherwise, no allocation of the identity information.

Preferably, the other mobility management entity judges whether a loadof the mobility management entity is greater than a predeterminedthreshold value and determines, when the load is greater than thethreshold value, not allocation of the identity information and,otherwise, allocation of the identity information.

The wireless communication system and a method for establishing aconnection between the UE and MME in the wireless communication systemaccording to the present invention to solve the above problem is capableof establishing a connection between the UE and the MME efficiently.That is, through the cooperation between the base station and the MME oramong the MMEs, it is possible to establish a connection between the UEand the MME efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a wirelesscommunication system according to an embodiment of the presentinvention,

FIG. 2 is a signaling diagram illustrating a connection procedure in thewireless communication system according to the first embodiment of thepresent invention,

FIG. 3 is a flowchart illustrating the operation procedure of the MME ofFIG. 2,

FIG. 4 is a flowchart illustrating the operation procedure of the eNB ofFIG. 2,

FIG. 5 is a signaling diagram illustrating a connection procedure in thewireless communication according to the second embodiment of the presentinvention,

FIG. 6 is a flowchart illustrating the operation procedure of the normalMME of FIG. 5,

FIG. 7 is a flowchart illustrating the operation procedure of the MTCMME of FIG. 5,

FIG. 8 is a signaling diagram illustrating a connection procedure in thewireless communication system according to the third embodiment of thepresent invention,

FIG. 9 is a flowchart illustrating the operation procedure of the normalMME of FIG. 8,

FIG. 10 is a signaling diagram illustrating a connection procedure inthe wireless communication system according to the fourth embodiment ofthe present invention,

FIG. 11 is a flowchart illustrating the operation procedure of thenormal MME of FIG. 10,

FIG. 12 is a signaling diagram illustrating the connection procedure inthe wireless communication system according to the fifth embodiment ofthe present invention,

FIG. 13 is a flowchart illustrating the operation procedure of thenormal MME of FIG. 12,

FIG. 14 is a flowchart illustrating the operation procedure of the eNBof FIG. 12,

FIG. 15 is a signaling diagram illustrating a connection procedure inthe wireless communication system according to the sixth embodiment ofthe present invention,

FIG. 16 is a flowchart illustrating the operation procedure of thenormal MME of FIG. 15, and

FIG. 17 is a flowchart illustrating the operation procedure of the eNBof FIG. 15.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. Detailed description of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the present invention.

FIG. 1 is a block diagram illustrating a configuration of a wirelesscommunication system according to an embodiment of the presentinvention.

Referring to FIG. 1, the wireless communication system of thisembodiment includes a UE 10, an enhanced Node B (eNB) 20, an MME 30, aServing Gateway (S-GW) 40, and a Packet Data Network Gateway (P-GW) 50.

The UE 10 may be fixed or mobile. The UE 10 can be a normal UE forperforming normal communication function or a Machine Type Communication(MTC) UE for performing MTC function. Here, MTC technology can beapplied to smart metering for automated communication between the powercompany server and electric meter reader and alarm system for automatedcommunication between the security company server and an illegalintrusion alarm.

The eNB 20 manages a cell. At this time, the eNB 20 is a macro eNB, andthe cell is a macro cell as a cell of a typical cellular system. Here,the terms “eNB” and “cell” can be interchangeably used in the samemeaning. The eNB 20 connects to the UE 10 through a radio channel andcontrols radio resource. For example, the eNB generates and broadcastssystem information necessary for control within the cell and allocatesradio resource for transmitting/receiving packet data or controlinformation to/from the UE 10. The system information is capable ofincluding carrier information (PLMN ID), eNB Cell Global ID (ECGI), andTracking Area ID (TAI) of each cell. The eNB is capable of collectingchannel measurement result information for the serving and neighborcells to make a handover decision and command handover. In order toachieve this, the eNB 20 is provided with the control protocol such asRadio Resource Control Protocol related to the radio resourcemanagement.

The MME 30 manages UE 10 in idle mode and selects the S-GW 40 and theP-GW 50. The MME 30 is responsible for roaming and authenticationfunctions. The MME 30 also processes bearer signals generated by the UE10. In order to achieve this, the MME 30 allocates identity informationto the UE 10 and manages the connection with the UE 10 using theidentity information. At this time, the MME 30 can be a normal MME forsupporting the normal UEs or a MTC MME for supporting the MTC UEs. Here,the MME 30 is cable of having a unique entity ID which allows foridentifying the normal MME and MTC MME.

The MME 30 connects to the eNB 20 through a radio channel and connectsto the UE 10 via the eNB 20. Here, the MME 30 connects to the eNB viaS1-MME interface. At this time, the MME 30 communicates with the UE 10using Non Access Stratum (NAS) message. The MME 30 supports a pluralityof tracking areas and is connected with a plurality of eNBs 20 providingrespective tracking area information. That is, a plurality of eNBs 20providing the same tracking area information can be connected with theMME 30. It is also possible for the plural eNBs 20 proving differenttracking area informations to connect to the respective MMEs 30. It isalso possible for the plural eNBs 20 supporting different tracking areasto be connect to the same MME 30.

The S-GW 40 connects to the eNB 20 and the MME 30 through radiochannels. Here, the S-GW 40 connects to the eNB 20 through S1-Uinterface. The S-GW 320 is responsible for the UE mobility controlfunction. That is, when the UE 10 performs handover between eNBs orroams across 3gpp radio network networks, the S-GW 40 acts as a mobilityanchor of the UE 10.

The P-GW 50 connects to the S-GW 40 through a radio channel. Here, theP-GW 50 connects to the S-GW via S5 interface. The P-GW 50 connects tothe Internet Protocol (IP) network 60. The P-GW 50 is responsible for IPaddress allocation to the UE 10 and packet data-related functions. Thatis, the P-GW 50 delivers the packet data received through the IP network60 to the UE 10 via the S-GW 40 and the eNB 20. When the UE movesbetween the 3GPP radio network and non-3GPP radio network, the P-GW 50acts as the mobility anchor of the UE 10. The P-GW 50 also determinesthe bearer bandwidth for the UE 10 and performs packet data forward androuting function.

The wireless communication system is capable of further including a HomeSubscriber Server (HSS) (not shown). The HSS stores the subscriberinformation per UE. When the UE 10 attempts attachment to the network,the HSS provides the MME 30 with the information related to the UE 10for use in controlling the UE 10.

Once it has connected to the eNB 20 of the wireless communicationsystem, the UE 10 connects to the IP network 60 through a data pathconsisting of the eNB 20, the S-GW 40, and the P-GW 50 so as to exchangepacket data. The UE 10 is also capable of transmitting a NAS request tothe MME 30 via the eNB 20. The NAS message is capable of includingrequest including at least one of attach request, tracking area updaterequest, or service request. Upon receiving the NAS request message, theeNB 20 selects MME 30 according to the Network Node Selection Function(NNSF) and sends the NAS request message to the selected MME 30. This isbecause the eNB 20 is capable of being connected to a plurality of MMEs30 individually through S1-MME interface.

In this embodiment, although the description is directed to the casewhere the UE 10 is an MTC UE, the eNB 20 is connected to the respectivenormal MME and MTC MME, the present invention is not limited thereto.That is, although the normal UE is replaced by MTC UE implemented with aspecific function and the MME is replaced by MTC MME implemented tosupport other type of UE, the present invention is applicable.

FIG. 2 is a signaling diagram illustrating a connection procedure in thewireless communication system according to the first embodiment of thepresent invention.

Referring to FIG. 2, the connection procedure between the MTC UE 11 andMTC MME 330 starts in such a way that the MTC UE 11 establishes an RRCconnection with the eNB 20. When it attaches to the radio networkinitially or enters the cell supporting the tracking area information,the MTC UE 11 is capable of performing initial RRC connection to the eNB20 to establish the connections to the MMEs 30, 31, and 33.

The MTC UE 11 sends the eNB 20 an RRC Connection Request message at step111. Since it is the initial connection to the eNB 20, the MTC UE 11sends the UE ID in the form of a Random Value through in the RRCconnection request message. Upon receipt of the RRC connection requestmessage, the eNB 20 sends the MTC UE 11 an RRC Connection Setup messageat step 113. Upon receipt of the RRC Connection Setup message, the MTCUE 11 sends the eNB 20 an RRC Connection Setup Complete message at step115. At this time, the MTC UE 11 transmits the NAS request message tothe MTC MME 33 in the RRC Connection Setup Complete message. Here, theMTC UE 11 is capable of transmitting the RRC Connection Request messageor the RRC Connection Setup Complete message with an MTC indicator forindicating that the UE is the MTC UE. The MTC UE 11 is also capable ofinserting the entity ID of the MME entity 30, 31, or 33 to which it hasconnected previously in the RRC Connection Setup Complete message.

Once the connection has been established with the MTC UE 11, the eNB 20selects one of a plurality of MMEs 30, 31, and 33 at step 117. At thistime, the eNB 20 determines whether the RRC Connection Setup Completemessage includes an entity ID. If an entity ID is included, the eNBselects the MME identified by the entity ID. If no entity ID isincluded, the eNB 20 selects an MME 30, 31, or 33 arbitrarily. If it hasno S1-MME interface connection with the MME identified by the entity ID,the eNB 20 selects an MME 30, 31, or 33 arbitrarily. Here, the eNB 20 iscapable of determining whether the RRC Connection Request message or theRRC Connection Setup Complete message includes the MTC indicator. If noMTC indicator is included, the eNB 20 selects the normal MME 31.Otherwise, if the MTC indicator is included, the eNB 20 selects the MTCMME 33.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 33an Initial UE message for the MTC UE 11 at step 119. At this time, theeNB 20 transmits the RRC Connection Setup Complete message in the NASRequest message. Upon receipt of the Initial UE Request message, the MTCMME 33 sends the MTC UE 11 an Initial UE Response message at step 121via the eNB 20. At this time, the MTC MME 33 generates the NAS Responsemessage by processing the request data in the NAS Request message. TheMTC MME 33 also transmits the NAS Response message in the NAS message.The MTC MME 33 is capable of transmitting Global Unique Temporary ID(GUTI) as the identity information for the MTC UE 11 in the NAS responsemessage. Here, the GUTI includes the information on the carriersupported by the eNB 20 connected currently to the MTC MME 33, MME GroupID of the MME 33, entity ID of the MTC MME 33, and MME-Temporary MobileSubscriber ID (M-TMSI) which the MTC MME 33 allocates to the MTC UE 11;and the SAE Temporary Mobile Subscriber ID consists of the entity ID andM-TMSI.

Meanwhile, the MTC UE 11 is capable of re-attempting RRC connection withthe eNB 20. That is, when it transitions from the idle mode to theactive mode or enters a cell supporting the tracking area informationthat has been identified already, the MTC UE 11 is capable of attemptingRRC connection to the eNB 20 for re-establishing the connection to theMME 30, 31, or 33 to which it has connected.

That is, the MTC UE 11 sends the eNB 20 the RRC Connection Requestmessage at step 141. Since it is a retry for connection to the eNB 20,the MTC UE 11 includes the S-TMSI as the UE ID in the RRC ConnectionRequest message. Upon receipt of the RRC Connection Request message, theeNB 20 sends the MTC UE 11 the RRC Connection Setup message at step 143.Upon receipt of the RRC Connection Setup message, the MTC UE 11 sendsthe eNB 20 the RRC Connection Setup Complete message at step 145. Atthis time, the MTC UE 11 transmits the NAS Request message for the MTCMME 33 in the RRC Connection Setup Complete message.

Once the MTC UE 11 has connected, the eNB 20 selects one of the pluralMMEs 30, 31, and 33 at step 147. At this time, the eNB 20 determineswhether the RRC Connection Setup Complete message includes the entityID. If the entity ID is included, the eNB 20 selects the MME identifiedby the entity ID. That is, the eNB 20 checks the entity ID with S-TMSIincluded in the RRC Connection Request message and selects the entitymatched with the entity ID. If no entity ID is included, the eNB 20selects an MME 30, 31, or 33 arbitrarily. In case that it has not S1-MMEinterface connection with the MME identified by the entity ID, the eNB20 selects an MME 30, 31, or 33 arbitrarily.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 33an Initial UE Request message for the MTC UE 11 at step 149. At thistime, the eNB 20 transmits the NAS Request message carried in the RRCConnection complete message. Upon receipt of the Initial UE requestmessage, the MTC MME 33 sends the MTC UE 11 an Initial UE Responsemessage via the eNB 20 at step 151. At this time, the MTC MME 33generates the NAS Response message by processing the request data in theNAS Request message. The MTC MME 33 transmits the NAS message includingthe NAS Response message.

The operation procedure between the MME 30, 31, and 33 and the eNB 20according to an embodiment of the present invention is describedhereinafter.

FIG. 3 is a flowchart illustrating the operation procedure of the MME30, 31, or 33 of FIG. 2.

Referring to FIG. 3, if a NAS request message is received from the UE 10or 11, the MME 30, 31, or 33 detects this at step 161 and determineswhether to assign GUTO to the UE 10 or 11 at step 163. That is, the MME30, 31, or 33 determines whether the GUTI has been assigned to the UE 10or 11. If it is determined that the GUTI has not been assigned to the UE10 or 11 at step 163, the MME 30, 31, or 33 assigns a GUTI to the UE 10or 11 at step 165. The MME 30, 31, or 33 also sends the UE 10 or 11 theNAS Response message including the corresponding GUTI at step 167.

Otherwise, if it is determined that the GUTO has been assigned to the UE10 or 11, the MME 30, 31, or 33 sends the UE 10 or lithe NAS Responsemessage via the eNB 20.

FIG. 4 is a flowchart illustrating the operation procedure of the eNB 20of FIG. 2.

Referring to FIG. 4, the eNB 20 of the present embodiment establishes anRRC connection with the UE 10 or 11 at step 181. If a NAS requestmessage is received from the UE 10 or 11, the eNB 20 detects the messageand selects an MME 30, 31, or 33 at step 185. If an entity IE isreceived along with the NAS request message, the eNB 20 selects the MME30, 31, or 33 matched with the entity ID. If no entity ID is received,the eNB 20 selects an MME 30, 31, or 33 arbitrarily. If an MTC indicatoris received along with the NAS request message, the eNB 20 selects theMTC MME 33. Otherwise, if no MTC indicator is received, the eNB 20selects the normal MME 31. The eNB 20 sends the MME 30, 31, or 33 theNAS request message at step 187. If the NAS Response message is receivedfrom the MME 30, 31, 33, the eNB 20 detects this at step 189 anddelivers the NAS response message to the UE 10 or 11 at step 191.

Although the above description has been directed to the exemplary casewhere the eNB 20 selects the MTC MME 33 for the MTC UE 11 in initial RRCconnection with the MTC UE 11 in the first embodiment of the presentinvention, the present invention is not limited thereto. That is, whenselecting an MME 30, 31, or 33 arbitrarily, although the eNB 20 selectsthe normal MME 31, the present invention can be implemented. Suchexamples are described in the second to sixth embodiments of the presentinvention.

FIG. 5 is a signaling diagram illustrating a connection procedure in thewireless communication according to the second embodiment of the presentinvention.

Referring to FIG. 5, the connection establishment procedure between theMTC UE 11 and the MTC MME 33 according the present embodiment starts insuch a way that the MTC UE 11 attempts to establish an RRC connection tothe eNB 20. When it attempts initial attachment to the radio network orenters a cell supporting the tracking area information, the MTC UE 11 iscapable of establishing the initial RRC connection to the eNB 20 toconnect to a new MME 30, 31, or 33.

The MTC UE 11 sends the eNB 20 an RRC connection request message at step211. Since it is the initial connection to the eNB 20, the MTC UE 11transmits a random value of the UE ID in the RRC connection requestmessage. If the RRC connection request message is received, the eNB 20sends an RRC connection setup message to the MTC UE 11 at step 213. Inresponse to the RRC connection setup message, the UE 11 sends an RRCconnection complete message to the eNB 20 at step 215. At this time, theMTC UE 11 transmits an NAS request message for the MTC MME 33 in the RRCconnection complete message. Here, the MTC UE 11 is capable of insertingthe entity ID of the MME 30, 31, or 33 to which it has connected in theRRC connection complete message.

If the MTC UE 11 has connected, the eNB 20 selects one of a plurality ofMMEs 30, 31, and 33 at step 217. At this time, the eNB 20 determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME 30, 31, or 33identified by the entity ID. Otherwise, if no entity ID is included, theeNB 20 selects an MME 30, 31, or 33 arbitrarily. If there is noconnection with the MME 30, 31, or 33 through the S1-MME interface, theeNB 20 selects an MME 30, 31, or 33 arbitrarily.

If the selected MME is the normal MME 31, the eNB 20 sends the normalMME 31 an initial UE request message for the MTC UE 11 at step 219. Atthis time, the eNB 20 transmits the NAS request message carried in theRRC connection complete message. If the initial UE request message inreceived, the normal MME 31 checks that the NAS request message istransmitted from the MTC UE 11 in the initial UE request message at step221. For example, the eNB 20 delivers the MTC indicator received fromthe MTC UE 11 to the normal MME 31 such that the normal MME 31identifies the MTC UE 11. Also, it is possible for the normal MME 31 toidentify the MTC UE 11 based on the MTC indicator included in thesubscriber information of the MTC UE 11 which is transmitted by the HSS.Also, it is possible for the normal MME 31 to identify the MTC UE 11based on the random value selected in the range allowed for normal UE asUE ID.

Next, the normal MME 31 sends a GUTI allocation request message to theMTC MME 33 at step 223. That is, the normal MME 31 requests the MTC MME33 for the GUTI of the MTC UE 11. In response to the GUTI allocationrequest message, the MTC MME 33 sends the normal MME 31 a GUTIallocation response message at step 225. That is, the MTC MME 33provides the normal MME 331 with the GUTI as the identity informationfor the MTC UE 11. Here, the GUTI includes the information on thecarrier supported by the eNB 20 connected currently to the MTC MME 33,MME Group ID of the MME 33, entity ID of the MTC MME 33, andMME-Temporary Mobile Subscriber ID (M-TMSI) which the MTC MME 33allocates to the MTC UE 11; and the S-TMSI consists of the entity ID andM-TMSI. If the GUTI allocation response message is received, the normalMME 31 is capable of transmits UE context of the MTC UE 11 to the MTCMME 33 at step 227.

Next, the normal MME 31 sends the MTC UE 11 an initial UE responsemessage via the eNB 20 at step 229. At this time, the normal MME 31generates the NAS response message by processing the request dataincluded in the NAS request message. The normal MME 31 also includes theGUTI for the MTC UE 11 in the NAS response message.

Meanwhile, the MTC UE 11 is capable of retries RRC connection to the eNB20. That is, when it wakes up and transitions from the idle mode to theactive mode or enters the cell supporting the tracking area informationthat has been identified already, the MTC UE 11 is capable of retryingRRC connection to the eNB 20 for reconnection to the MME 30, 31, or 33.

That is, the MTC UE 11 transmits the RRC connection request message tothe eNB 20 at step 241. Since it is the retry for connection, the MTC UE11 transmits the RRC connection request message configured with theS-TMSI as the UE ID. If the RRC connection request message is received,the eNB 20 sends the MTC UE 11 the RRC connection setup message at step243. If the RRC connection setup message is received, the MTC UE 11sends the RRC connection complete message to the eNB 20 at step 245. Atthis time, the MTC UE 11 transmits the NAS request message for the MTCMME 33 in the RRC connection complete message.

Once the MTC UE 11 has connected, the eNB 20 selects one of the pluralMMEs 30, 31, or 33 at step 247. At this time, the eNB 20 determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME identified by theentity ID. That is, the eNB 20 checks the entity ID based on the S-TMSIincluded in the RRC connection request message and selects the MME 30,31, or 33 matched to the entity ID. If not entity ID is included, theeNB selects an MME 30, 31, or 33 arbitrarily. If there is no connectionwith the MME 30, 31, or 33 matched to the entity ID through S1-MMEinterface, the eNB 20 selects an MME 30, 31, or 33 arbitrarily.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 22the initial UE request message for the MTC UE 11 at step 249. Here, theeNB 20 transmits the NAS request message in the RRC connection completemessage. If the initial UE request message is received, the MTC MME 33is capable of sending the normal MME 31 a UE context request message forthe MTC UE 11 at step 251. If the UE context request message isreceived, the normal MME 31 is capable of sending the MTC MME 33 a UEcontext response message including the UE context at step 253.Afterward, the MTC MME 33 sends the MTC UE 11 the initial UE responsemessage via the eNB 20 at step 255. At this time, the MTC MME 33generates the NAS message by processing the request data included in theNAS request message. The MTC MME 33 also transmits the NAS responsemessage in the NAS message.

Descriptions are made of the operation procedures of the normal MME 31and MTC MME 33 hereinafter. Since the operation procedure of the eNB 20in the present embodiment is similar to that of the first embodiment ofthe present invention, detailed description thereon is omitted herein.

FIG. 6 is a flowchart illustrating the operation procedure of the normalMME 31 of FIG. 5.

Referring to FIG. 6, if an NAS request message is received from the UE10 or 11, the normal MME 31 detects this at step 261 and determineswhether to allocate GUTI to the UE 10 or 11 at step 263. That is, thenormal MME 31 determines whether the UE 10 or 11 has been assigned theGUTI already. If it is determined to allocate GUTI at step 263, thenormal MME 31 determines whether the UE 10 or 11 is the MTC UE 11 atstep 265. If it is determined that the UE 10 or 11 is the MTC UE 11 atstep 265, the normal MME 31 sends the MTC MME 33 a GUTI allocationrequest message at step 267. Afterward, if a GUTI allocation responsemessage is received from the MTC MME 33, the normal MME 31 detects thisat step 269 and sends the UE 10 or 11 a NAS response message includingthe corresponding GUTI at step 271.

Otherwise, if it is determined that the UE 10 or 11 is not the MTC UE 11at step 265, the normal MME 31 allocates a GUTI to the UE 10 or 11 atstep 270. Next, the normal MME 31 sends the UE 10 or 11 the NAS responsemessage including the GUTI at step 271. If it is determined that thereis no need to allocate GUTI to the UE 10 or 11 at step 263, the normalMME 31 sends the UE 10 or 11 a NAS response message via the eNB 20 atstep 275.

FIG. 7 is a flowchart illustrating the operation procedure of the MTCMME 33 of FIG. 5.

Referring to FIG. 7, if a GUTI allocation request message is receivedfrom the normal MME 31, the MTC MME 33 detects this at step 281 andsends the normal MME 31 a GUTI allocation response message at step 283.If no GUTI allocation request message is received but a NAS requestmessage is received from the UE 10 or 11, the MTC MME 33 detects this atstep 285 and sends the UE 10 or 11 the NAS response message via the eNB20 at step 287.

Although the description has been directed to the case where the normalMME 31 and MTC MME 33 communicate to each other directly in the secondembodiment of the present invention, the present invention is notlimited thereto. That is, even when the normal MME 31 and the MTC MME 33are not communication directly, the present invention can beimplemented. Such an example is described in the third embodiment of thepresent invention hereinafter.

FIG. 8 is a signaling diagram illustrating a connection procedure in thewireless communication system according to the third embodiment of thepresent invention.

Referring to FIG. 8, the connection procedure between the MTC UE 11 andthe MTC 33 according to the third embodiment starts in such a way thatthe normal MME 31 retains the list of GUTIs, i.e. MTC GUTIs, as theidentity information that can be allocated by the MTC MME 33 at step311. At this time, the MTC MME 33 sends the list of the MTC GUTIsdirectly to the normal MME 31 such that the normal MME 31 stores the MTCGUTI list. The MTC MME 33 registers the MTC GUTI list with an Operationand Management (O&M) server (not shown) which provides the normal MME 31with the MTC GUTI such that the normal MME 31 is capable of storing thelist of the MTC GUTIs. Here, the GUTI includes the information on thecarrier supported by the eNB 20 connected currently to the MTC MME 33,MME Group ID of the MME 33, entity ID of the MTC MME 33, andMME-Temporary Mobile Subscriber ID (M-TMSI) which the MTC MME 33allocates to the MTC UE 11; and the S-TMSI consists of the entity ID andM-TMSI.

Next, the MTC UE 11 attempts the RRC connection to the eNB 20. When itattempts initial attachment to the radio network or enters the cellsupporting the tracking area information, the MTC UE 11 is capable ofattempting the initial RRC connection to the eNB 20 to establishingconnection to the MME 30, 31, or 33.

That is, the MTC UE 11 sends the eNB 20 an RRC connection requestmessage at step 313. Since it is the initial attachment to the eNB 20,the MTC UE 11 sends a random value as the UE ID in the RRC connectionrequest message. If the RRC connection request message is received, theeNB 20 sends the MTC UE 11 an RRC connection setup message at step 315.In response to the RRC connection setup message, the MTC UE 11 sends theeNB 20 an RRC connection complete message at step 317. At this time, theMTC UE 11 transmits a NAS request message for the MTC MME 33 in the RRCconnection complete message. Here, the MTC UE 11 is capable of furtherincluding the entity ID of the MME 30, 31, or 33 to which it hasconnected previously in the RRC connection complete message.

Once the MTC UE 11 has connected, the eNB 20 selects one of the pluralMMEs 30, 31, and 33 at step 319. At this time, the eNB 20 determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME 30, 31, or 33 matchedwith the entity ID. Otherwise, if no entity ID is included, the eNB 20selects an MME 30, 31, or 33 arbitrarily. If it is not connected to theMME 30, 31, or 33 match with the entity ID through S1-MME interface, theeNB selects an MME 30, 31, or 33 arbitrarily.

If the normal MME 31 is selected, the eNB 20 sends the normal MME 31 aninitial UE request message addressed to the MTC UE 11 at step 321. Atthis time, the eNB 20 transmits the NAS request message carried in theRRC connection complete message. If the initial UE request message isreceived, the normal MME 31 checks that the NAS message carried in theinitial UE request message has been transmitted by the MTC MME 11 atstep 323. For example, the eNB 20 transmits the MTC indicator receivedfrom the MTC UE 11 to the normal MME 31 such that the normal MME 31identifies the MTC UE 11. Also, it is possible for the HSS to transmitthe MTC indicator in the subscriber information of the MTC UE 11 to thenormal MME 31 such that the normal MME 31 identifies the MTC UE 11.Also, it is possible for the MTC UE 11 uses a random value selected inthe range discriminated from that for the normal UE such that the normalMME 31 identifies the MTC UE 11. The normal MME 31 determines the GUTIfor the MTC UE 11 from the MTC GUTI list and marks the GUTI as beingused at step 324. The normal MME 31 is capable of transmitting the UEcontext of the MTC UE 11 to the MTC MME 33 at step 325 and then checkingthat the GUTI for the MTC UE 11 is not used from the MTC GUTI list atstep 326.

Next, the normal MME 31 sends the MTC UE 11 an initial UE responsemessage via the eNB 20 at step 327. At this time, the normal MME 31generates a NAS response message by processing the request data in theNAS request message. The normal MME 31 transmits the NAS responsemessage in the NAS message. The normal MME 31 is also capable oftransmitting the GUTI selected from the MTC GUTI list in the NASresponse message.

The MTC UE 11 is capable of retrying the RRC connection to the eNB 20.After wake-up from the idle mode when it transitions from the idle modeto the active mode or enters the cell supporting the tracking areainformation that has been identified already, the MTC UE 11 is capableof retrying the RRC connection to the eNB 20 to reestablish theconnection to the MME 30, 31, or 33 to which it has connectedpreviously.

That is, the MTC UE 11 sends the eNB 20 an RRC connection requestmessage at step 341. Since it is the retry of the connection to the eNB20, the MTC UE 11 transmits the RRC connection request message with theS-TMSI as the UE ID. If the RRC connection request message is received,the eNB 20 sends the MTC UE 11 an RRC connection setup message at step343. In response to the RRC connection setup message, the MTC UE 11sends the eNB 20 an RRC connection complete message at step 345. At thistime, the MTC UE 11 transmits the NAS request message for the MTC MME 33in the RRC connection complete message.

If the MTC UE 11 has connected, the eNB 20 selects one of the pluralMMEs 30, 31, and 33 at step 347. At this time, the eNB determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME 30, 31, or 33 matchedwith entity ID. That is, the eNB 20 checks the entity ID based on theS-TMSI included in the RRC connection request message and selects theMME 30, 31, or 33 matched with the entity ID. If no entity ID isincluded, the eNB 20 selects an MME 30, 31, or 33 arbitrarily. Also, ifit has not connected to the MME 30, 31, or 33 matched with the entity IDthrough S1-MME interface, the eNB 20 selects an MME 30, 31, or 33arbitrarily.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 33an initial UE request message for the MTC UE 11 at step 349. Here, theeNB 20 transmits the NAS request message carried in the RRC connectioncomplete message. If the initial UE request message is received, the MTCMME 33 is capable of transmitting a UE context request message for theMTC UE 11 to the normal MME 31 at step 351. If the UE context requestmessage is received, the normal MME 31 sends the MTC MME 33 a UE contextresponse message including the UE context at step 353 and marks the GUTIfor the MTC UE 11 as not being used in the MTC GUTI list at step 354.Although not depicted, when the UE context request message is received,the normal MME 31 is capable of checking the GUTI for the MTC UE 11 asbeing not used in the MTC GUTI list and then transmits the UE contextresponse message. Afterward, the MTC MME 33 sends the MTC UE 11 aninitial UE response message via the eNB 20 at step 355. At this time,the MTC MME 33 generates the NAS response message by processing therequest data in the NAS request message. The MTC MME 33 transmits theNAS response message in the NAS message.

A description is made of the operation procedure of the normal MME 31according to this embodiment hereinafter. Since the operation proceduresof the eNB 20 and the MTC MME 33 according to this embodiment aresimilar to those in the first embodiment, detailed descriptions thereonare omitted herein.

FIG. 9 is a flowchart illustrating the operation procedure of the normalMME 31 of FIG. 8.

Referring to FIG. 9, the normal MME 31 retains the MTC GUTI list in theembodiment at step 361. At this time, the normal MME 31 also stores alist of GUTIs that the normal MME 31 can allocate, i.e. normal GUTI listin addition to the MTC GUTI list. If a NAS request message is receivedfrom the UE 10 or 11, the normal MME 31 detects this and determineswhether to allocate GUTI to the UE 10 or 11 at step 363. That is, thenormal MME 31 determines whether it has allocated a GUTI to the UE 10 or11 previously. If it is determined to allocate a GUTI to the UE 10 or 11at step 365, the normal MME 31 determines whether the UE 10 or 11 is anMTC UE 11 at step 367. If it is determined that the UE 10 or 11 is theMTC UE 11 at step 367, the normal MME 31 allocates an GUTI selected fromthe MTC GUTI list to the UE 10 or 11. Afterward, the normal MME 31 sendsthe UE 10 or 11 a NAS response message including the corresponding GUTIat step 371.

Otherwise, if it is determined that the UE 10 or 11 is not the MTC UE 11at step 367, the normal MME 31 allocates the GUTI selected from thenormal GUTI rest to the UEs 10 or 11 at step 370. Next, the normal MME31 sends the UE 10 or 11 the NAS response message including thecorresponding GUTI at step 371. If it is not necessary to allocate aGUTI to the UE 10 or 11 at step 365, the normal MME 31 sends the UE 10or 11 the NAS response message via the eNB 20 at step 375.

Although the description has been directed to the case where normal MME31 delivers the GUTI allocated by the MTC MME 33 to the MTC UE 11 in theinitial RRC connection between the MTC UE 11 and the eNB 20 in thesecond and third embodiments, the present invention is not limitedthereto. That is, the present invention can be implemented in such a waythat the MTC MME 33 is capable of allocating and transmitting the GUTIfor the MTC UE 11. Such an example is described hereinafter in thefourth embodiment of the present invention.

FIG. 10 is a signaling diagram illustrating a connection procedure inthe wireless communication system according to the fourth embodiment ofthe present invention.

Referring to FIG. 10, the connection procedure between the MTC UE 11 andthe MTC MME 33 according to the this embodiment starts in such a waythat the MTC UE 11 attempts RRC connection to the eNB 20. At this time,when it tries initial attachment to the radio network or enters the cellsupporting the tracking area information, the MTC UE 11 is capable ofinitial RRC connection to the eNB 20 to establish the connection to anew MME 30, 31, or 33.

That is, the MTC UE 11 sends the eNB 20 the RRC connection requestmessage at step 411. Since it is the initial attachment, the MTC UE 11transmits a random value as the UE ID in the RRC connection requestmessage. If the RRC connection request message is received, the eNB 20sends the MTC UE 11 an RRC connection setup message at step 413. If theRRC connection setup message is received, the MTC UE 11 sends an RRCconnection complete message to the eNB 20 at step 415. At this time, theMTC UE 11 transmits a NAS request message for the MTC MME 33 in the RRCconnection complete message. here, the MTC UE 11 is capable of furtherincluding the entity ID of the MME 30, 31, or 33 to which is hasconnected previously in the RRC connection complete message.

Once the MTC UE 11 has connected, the eNB 20 selects one of a pluralityof MMEs 30, 31, and 33 at step 417. At this time, the eNB 20 determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME 30, 31, or 33 matchedwith the entity ID. If no entity ID is included, the eNB 20 selects anMME 30, 31, or 33 arbitrarily. Also, if it has not connected to the MME30, 31, or 33 matched with the entity ID via S1-MME interface, the eNB20 selects an MME 30, 31, or 33 arbitrarily.

Once the normal MME 31 has been selected, the eNB 20 sends the normalMME 31 an initial UE request message for the MTC UE 11 at step 419. Atthis time, the eNB 20 transmits the NAS request message carried in theRRC connection complete message. If the initial UE request message isreceived, the normal MME 31 determines whether the NAS request messagecarried in the initial UE request message is transmitted by the MTC UE11 at step 421. For example, the eNB 20 transmits the MTC indicatorreceived from the MTC UE 11 to the normal MME 31 such that the normalMME 31 identifies the MTC UE 11. Also, it is possible for the HSS totransmit the MTC indicator in the subscriber information of the MTC UE11 such that the normal MME 31 identifies the MTC UE 11. Also, it ispossible for the MTC UE 11 to use a random value selected in the rangediscriminated from that for the normal UE such that the normal MME 31identifies the MTC UE 11.

Next, the normal MME 31 sends the MTC MME 33 an initial UE requestmessage for the MTC UE 11 at step 423. Here, the normal MME 31 iscapable of transmitting the initial UE request message using thetunneling technique. If the initial UE request message is received, theMTC MME 33 is capable of transmitting to the normal MME 31 a UE contextrequest message for the MTC UE 11 additionally at step 425. If the UEcontext request message is received, the normal MME 31 is capable oftransmitting a UE context response message including the UE context tothe MTC MME 33 at step 427. Here, the MTC MME 33 and the MTC UE 11 arecapable of perform NAS communication via the eNB 20 and the normal MME31 at step 429. That is, the MTC MME 33 and the MTC UE 11 are capable ofgenerating and exchanging NAS messages. Here, the normal MME 31 iscapable of exchanging the NAS messages with the MTC MME 33 using thetunneling technique.

Next, the MTC MME 33 sends the normal MME 31 an initial UE responsemessage at step 431. At this time, the MTC MME 33 generates the NASresponse message by processing the request data in the NAS requestmessage. Here, the MTC MME 33 is capable of transmitting the NASresponse message using the tunneling technique. The MTC MME 33 iscapable of transmitting the GUTI allocated as identity information ofthe MTC UE 11 in the NAS response message. Afterward, if the initial UEresponse message is received, the normal MME 31 transmits the initial UEresponse message to the MTC UE 11 via the eNB 20 at step 433.

Meanwhile, the MTC UE 11 is capable of retrying RRC connection to theeNB 20. After wake-up from the idle mode, when it transitions from theidle mode to the active mode or enters the cell supporting the trackingarea information which has been known already, the MTC UE 11 is capableof retrying the RRC connection to the eNB 20 for reestablishing theconnection to the MME 30, 31, or 33 to which the MTC MME has connectedpreviously.

That is, the MTC UE 11 sends the eNB 20 the RRC connection requestmessage at step 441. Since it is reconnection to the eNB 20, the MTC UE11 transmits the RRC connection request message in which the UE ID isset to the S-TMSI. If the RRC connection request message is received,the eNB 20 sends the MTC UE 11 an RRC connection setup message at step443. If the RRC connection setup message is received, the MTC UE 11sends the eNB 20 an RRC connection complete message at step 445. At thistime, the MTC UE 11 transmits the NAS request message for the MTC MME 33in the RRC connection complete message.

Once the MTC terminal 11 has connected, the eNB 20 selects one of theplural MMEs 30, 31, and 33 at step 447. At this time, the eNB 20determines whether the RRC connection complete includes an entity ID. Ifan entity ID is included, the eNB 20 selects the MME 30, 31, or 33matched with the entity ID. That is, the eNB 20 checks the entity IDfrom the S-TMSI of the RRC connection request message and selects theMME 30, 31, or 33 matched with the entity ID. Otherwise, if no entity IDis included, the eNB 20 selects an MME 30, 31, or 33 arbitrarily. Also,if it has not connected to the MME 30, 31, or 33 matched with the entityID, the eNB 20 selects an MME 30, 31, or 33 arbitrarily.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 33an initial UE request message for the MTC UE 11 at step 449. Here, theeNB 20 transmits the NAS request message carried in the RRC connectioncomplete message. If the initial UE request message is received, the MTCMME 33 sends the MTC UE 11 an initial UE response message via the eNB 20at step 451. At this time, the MTC MME 33 generates the NAS responsemessage by processing the request data in the NAS request message. TheMTC MME 33 transmits the NAS response message in the NAS message.

A description is made of the operation procedure of the normal MME 31according to this embodiment hereinafter. Since the operation proceduresof the eNB 20 and the MTC MME 33 according to this embodiment aresimilar to those of the first embodiment of the present invention,detailed descriptions thereon are omitted herein.

FIG. 11 is a flowchart illustrating the operation procedure of thenormal MME 31 of FIG. 10.

Referring to FIG. 11, if an NAS request message is received from the UE10 or 11, the normal MME 31 detects this at step 461 and determineswhether to allocate a GUTI to the UE 10 or 11 at step 463. That is, thenormal MME 31 determines whether the UE 10 or 11 has been allocated aGUTI already. If it is determined that the UE 10 or 11 has beenallocated a GUTI already at step 463, the normal MME 31 determineswhether the UE 10 or 11 is the MTC UE 11 at step 465. If it isdetermined that the UE 10 or 11 is the MTC UE 11 at step 465, the normalMME 31 sends the MTC MME 33 a NAS request message at step 467.Afterward, if an NAS response message including the GUTI for the UE 10or 11 is received, the normal MME 31 detects this at step 469 anddelivers the NAS response message including the corresponding GUTI tothe UE 10 or 11 at step 471.

Otherwise, if it is determined that the UE 10 or 11 is not the MTC UE 11at step 465, the normal MME 31 allocates a GUTI for the UE 10 or 11 atstep 470. The normal MME 31 delivers the NAS response message to the UE10 or 11 at step 471. At this time, the normal MME 31 transmits the NASresponse message including the corresponding GUTI. If it is determinedthat there is no need to allocate a GUTI to the UE 10 or 11 at step 463,the normal MME 31 sends the UE 10 or 11 the NAS response message via theeNB 20.

Although the description is directed to the case, when the eNB 20selects the MME 30, 31, or 33 for the MTC UE 11, the MME 30, 31, or 33performs operation for allocating GUTI to the MTC 11 in the second tofourth embodiments of the present invention, the present invention isnot limited thereto. That is, the present invention is capable of beingimplemented in such a way that, as well as the MME 30, 31, or 33, theeNB 20 performs the operation for allocation GUTI to the MTC UE 11. Suchexamples are described in the fifth and sixth embodiments of the presentinvention hereinafter.

FIG. 12 is a signaling diagram illustrating the connection procedure inthe wireless communication system according to the fifth embodiment ofthe present invention.

Referring to FIG. 12, the connection procedure between the MTC UE 11 andthe MTC MME 33 according to this embodiment starts in such a way thatthe MTC UE 11 attempts RRC connection to the eNB 20. When it attemptsinitial connection to the radio network or enters a cell supporting thetracking area information which has not been recognized, the MTC UE 11is capable of attempting initial RRC connection to the eNB 20 toestablish the connection to a new MME 30, 31, or 33.

That is, the MTC UE 11 sends the eNB 20 an RRC connection requestmessage at step 511. Since it is the attempt for initial attachment tOthe eNB 20, the MTC UE 11 transmits the RRC connection request messageincluding a random value set as the UE ID. If the RRC connection requestmessage is received, the eNB 20 sends the MTC UE 11 an RRC connectionsetup message at step 513. If the RRC connection setup message isreceived, the MTC UE 11 sends the eNB 20 an RRC connection completemessage at step 515. At this time, the MTC UE 11 transmits the NASrequest message for the MTC MME 33 in the RRC connection completemessage. Here, the MTC UE 11 is capable of transmitting the RRCconnection complete message including the entity ID of the MME 30, 31,or 33 to which it has connected previously.

Once the MTC UE 11 has connected, the eNB 20 selects one of the pluralMMEs 30, 31, and 33 at step 517. At this time, the eNB determineswhether the RRC connection complete message includes an entity ID. If anentity ID is included, the eNB 20 selects the MME entity 30, 31, or 33matched with the entity ID. If no entity ID is included, the eNB 20selects an MME 30, 31, or 33 arbitrarily. Also, if it has not connectedto the MME 30, 31, or 33 matched with the entity ID via S1-MMEinterface, the eNB 20 selects an MME 30, 31, or 33 arbitrarily.

If the normal MME 31 has been selected, the eNB 20 sends the normal MME31 an initial UE request message for the MTC UE 11 at step 519. At thistime, the eNB 20 transmits the NAS request message carried in the RRCconnection complete message. Here, the eNB 20 is capable of storing theinitial UE request message or the NAS request message. If the initial UErequest message is received, the normal MME 31 checks that the NASrequest message carried in the initial UE request message has beentransmitted by the MTC UE 11 at step 521. For example, the eNB 20 iscapable of transmitting the MTC indicator received from the MTC UE 11 tothe normal MME 31 such that the normal MME 31 identifies the MTC UE 11.Also, it is possible for the HSS to transmit the MTC indicator in thesubscriber information of the MTC UE 11 such that the normal MME 31identifies the MTC UE 11. Also, it is possible for the MTC UE 11 to usea random value selected in the range discriminated from that for thenormal UE such that the normal MME 31 identifies the MTC UE 11.

Next, if the MTC UE 11 has been identified, the normal MME 31 sends theeNB 20 an MME reselection request (UE Redirect Request) message at step523. At this time, the normal MME 31 in capable of transmitting the MMEreselection request message including the information on the MTC MME 33,e.g. entity ID. Here, the normal MME 31 is capable of transmitting theNAS request message of the MTC UE 11 in the MME reselection requestmessage.

Next, if the MME reselection request message is received, the eNB 20selects one of the plural MMEs 30, 31, and 33 at step 525. At this time,the eNB selects the MTC MME 33. Herein, the eNB 20 determines whetherthe MME reselection request message includes an entity ID. If an entityID is included, the eNB 20 selects the MTC MME 33 matched to the entityID. Otherwise, if no entity ID is included, the eNB 20 selects an MTCMME 33 arbitrarily. Also, if it has not connected to the MME 33 matchedwith the entity ID via S1-MME interface, the eNB 20 selects the MTC MME33 arbitrarily.

Next, if the MTC MME 33 has been selected, the eNB 20 sends the MTC MME33 an initial UE request message for the MTC UE 11 at step 527. The MTCMME 33 sends the MTC UE 11 an initial UE response message via the eNB 20at step 529. At this time, the MTC MME 33 generates the NAS responsemessage by processing the request data in the NAS request message. TheMTC MME 33 transmits the NAS response message in the NAS message. TheMTC MME 33 is also capable of transmitting the NAS response messageincluding the GUTI allocated as the identity information of the MTC UE11.

The MTC UE 11 is capable of retrying RRC connection to the eNB 20. Thatis, after wake-up from the idle mode, when it transitions from the idlemode to the active mode or enters a cell supporting the tracking areainformation which has not been recognized until then, the MTC UE 11 iscapable of retrying RRC connection to the eNB 20 to reestablish theconnection to the MME 30, 31, or 33 to which it has connectedpreviously. Next, the MTC UE 11 is capable of attempting connection tothe MTC MME 33 via the eNB 20. Since the connection procedure betweenthe MTC UE 11 and the MTC MME 33 is similar to steps 441 to 451 of FIG.10, detailed description thereon is omitted herein.

Descriptions are made of the operation procedures of the normal MME 31and the eNB 20 according to the present embodiment hereinafter. Sincethe operation procedure of the MTC MME 33 according to this embodimentis similar to that of the first embodiment of the present invention,detailed description thereon is omitted herein.

FIG. 13 is a flowchart illustrating the operation procedure of thenormal MME 31 of FIG. 12.

Referring to FIG. 13, if the NAS request message is received from the UE10 or 11, the normal MME 31 detects this at step 561 and determineswhether to allocate a GUTI to the UE 10 or 11 at step 563. That is, thenormal MME 31 determines whether the UE 10 or 11 has been allocated aGUTI already. If it is determined to allocate a GUTI to the UE 10 or 11at step 563, the normal MME 31 determines whether the UE 10 or 11 is theMTC UE 11 at step 565. If it is determined that the UE 10 or 11 is theMTC UE 11, the normal MME 31 sends the eNB an MME reselection requestmessage at step 567.

Otherwise, if it is determined that the UE 10 or 11 is not the MTC UE 11at step 565, the normal MME 31 allocates a GUTI to the UE 10 or 11 atstep 569. Next, the normal MME 31 sends the UE 10 or 11 a NAS responsemessage at step 571. At this time, the normal MME 31 transmits the NASresponse message including the corresponding GUTI. If it is determinednot to allocate a GUTI to the UE 10 or 11 at step 563, the normal MME 31sends the UE 10 or 11 a NAS response message via the eNB 20 at step 573.

FIG. 14 is a flowchart illustrating the operation procedure of the eNB20 of FIG. 12.

Referring to FIG. 14, the eNB 20 tries to establish RRC connection withthe UE 10 or 11 at step 581. Afterward, if a NAS request message isreceived from the UE 10 or 11, the eNB 20 detects this at step 583 andselects an MME 30, 31, or 33 at step 585. At this time, if an entity IDis received in the NAS request message, the eNB 20 selects the MME 30,31, or 33 matched with the entity ID. If no entity ID is received, theeNB selects an MME entity 30, 31, or 33 arbitrarily. If an MTC indicatoris received in the NAS request message, the eNB 20 selects the MTC MME33. If no MTC indicator is received, the eNB 20 selects the normal MME31. The eNB 20 delivers the NAS request message to the MME 30, 31, or 33at step 587.

Next, if an MME reselection request message is received from the MME 30,31, or 33, the eNB 20 detects this at step 589 and reselects an MME 30,31, or 33 at step 591. At this time, the eNB 20 selects the MTC MME 33.At this time, if an entity ID is received in the MME reselection requestmessage, the eNB 20 selects the MTC MME 33 matched with the entity ID.If no entity ID is received, the eNB 20 selects the MTC MME 33arbitrarily. The eNB 20 delivers the NAS request message to thereselected MME 30, 31, or 33 at step 593.

Afterward, if a NAS response message is received from the MME 30, 31, or33, the eNB detects this at step 595 and delivers the NAS responsemessage to the UE 10 or 11 at step 597.

Although the description is directed to the case where the eNB 20retransmits the NAS request message in the fifth embodiment of thepresent invention, the present invention is not limited thereto. Thatis, the present invention can be implemented in such a way that the MTCUE 11 retransmits the NAS request message. Such an example is describedin the sixth embodiment of the present invention of the presentinvention.

FIG. 15 is a signaling diagram illustrating a connection procedure inthe wireless communication system according to the sixth embodiment ofthe present invention.

Referring to FIG. 15, the connection procedure between the MTC UE 11 andthe MTC MME 33 starts in such a way that the MTC UE 11 attempts RRCconnection to the eNB 20. At this time, when it attaches to the networkinitially or enters a cell supporting the tracking information which hasnot been recognized yet, the MTC UE 11 is capable of trying initial RRCconnection to the eNB 20 to establish a connection to a new MME 30, 31,or 33.

That is, the MTC UE 11 sends an RRC connection request message to theeNB 20 at step 611. Since it is the initial connection attempt to theeNB 20, the MTC UE 11 transmits a random value as a UE ID in the RRCconnection request message. If the RRC connection request message isreceived, the eNB 20 sends the MTC UE 11 an RRC connection setup messageat step 613. If the RRC connection setup message is received, the MTC UE11 sends the eNB 20 an RRC connection complete message at step 615. Atthis time, the MTC UE 11 transmits a NAS request message for the MTC MME33 in the RRC connection complete message. Here, the MTC UE 11 iscapable of transmitting the entity ID of the MME 30, 31, or 33 to whichit has connected previously in the RRC connection complete message.

Next, if the MTC UE 11 has connected, the eNB 20 selects one of aplurality of MMEs 30, 31, and 33 at step 617. At this time, the eNB 20determines whether the RRC connection complete message includes anentity ID. If an entity ID is included, the eNB 20 selects the MME 30,31, or 33 matched with the entity ID. If no entity ID is included, theeNB 20 selects an MME 30, 31, or 31 arbitrarily. Also, if it has notconnected with the MME 30, 31, or 33 matched with the entity ID throughS1-MME interface, the eNB 20 selects an MME 30, 31, or 33 arbitrarily.

Once the normal MME 31 has been selected, the eNB 20 sends the normalMME 31 an initial UE request message for the MTC UE 11 at step 619. Atthis time, the eNB 20 delivers the NAS request message carried in theRRC connection complete message. If the initial UE request message isreceived, the normal MME 31 checks that the NAS request message carriedin the initial UE request message has been transmitted by the MTC UE 11.For example, the eNB 20 transmits the MTC indicator received from theMTC UE 11 to the MME 31 such that the MME 31 identifies the MTC UE 11.Also, it is possible for the HSS to transmit the MTC indicator in thesubscriber information of the MTC UE 11 to the normal MME 31 such thatthe normal MME 31 identifies the MTC UE 11. Also, it is possible for theMTC UE 11 to use a random value selected in the range discriminated fromthat for the normal UE as the UE ID such that the normal MME 31identifies the MTC UE 11.

Next, if the MTC UE 11 has been identified, the normal MME 31 sends theeNB 20 a MME reselection request message at step 623. At this time, thenormal MME 31 is capable of the information or the MTC MME 33, i.e.entity ID, in the MME reselection request message. Afterward, the normal31 delivers the NAS retransmission request message to the MTC UE 11 atstep 625. At this time, the normal MME 31 is capable of the NASretransmission request message through NAS communication via the eNB 20.If the NAS retransmission request message is received, the MTC UE 11retransmits the NAS request for the MTC MME 33 at step 627. At thistime, the MTC UE 11 is capable of transmitting the NAS request messagethrough NAS communication.

Next, if the retransmitted NAS request message is received, the eNB 20selects one of the plural MMEs 30, 31, and 33 at step 629. At this time,the eNB 20 selects the MTC MME 33. Here, the eNB 20 determines whetherthe MME reselection request message includes an entity ID. If an entityID is included, the eNB selects the MTC MME 33 matched with the entityID. Otherwise, if no entity ID is included, the eNB 20 selects the MTCMME 33 arbitrarily. Also, if it has not connected to the MTC MME 33matched with the entity ID through the S1-MME interface, the eNB selectsthe MTC MME 33 arbitrarily.

Once the MTC MME 33 has been selected, the eNB 20 sends the MTC MME 33an initial UE request message for the MTC UE 11 at step 631. The MTC MME33 sends the MTC UE 11 an initial UE response message via the eNB 20 atstep 633. At this time, the MTC MME 33 generates the NAS responsemessage by processing the request data in the NAS request message. TheMTC MME 33 transmits the NAS response message in a NAS message. The MTCMME 33 is also capable of transmitting the NAS response messageincluding a GUTI allocated as the identifier information of the MTC UE11.

The MTC MME 11 is capable of retrying the RRC connection to the eNB 20.That is, when it wakes up, i.e. transitions from the idle mode to theactive mode or enters the cell supporting the tracking area informationwhich has been recognized previously, the MTC UE 11 is capable ofretrying the RRC connection to the eNB 20 to reestablish the connectionto the MME 30, 31, or 33 to which the MTC UE 11 has connectedpreviously. The MTC UE 11 is capable of trying to connect to the MTC MME33 via the eNB 20. Since the connection procedure between the MTC UE 11and the MTC MME 33 is similar to steps 441 to 451 of FIG. 10 that hasbeen described above, detailed description thereon is omitted herein.

The operation procedures of the normal MME 31 and the eNB 20 accordingto the present invention embodiment are described hereinafter. Since theoperation procedure of the MTC MME 33 according to the presentembodiment is similar to that of the first embodiment of the presentinvention, detailed description thereon is omitted herein.

FIG. 16 is a flowchart illustrating the operation procedure of thenormal MME 31 of FIG. 15.

Referring to FIG. 16, if a NAS request message is received from the UE10 or 11, the normal me 31 detects this at step 661 and determineswhether to allocate a GUTI to the UE 10 or 11 at step 663. That is, thenormal MME 31 determines whether the UE 10 or 11 has been allocated aGUTI already. If it is determined to allocate a GUTI to the UE 10 or 11at step 663, the normal MME 31 determines whether the UE 10 or 11 is theMTC UE 11 at step 665. If it is determined that the UE 10 or 11 is theMTC UE 11 at step 665, the normal MME 31 sends the eNB 20 an MMEreselection request message at step 667. Next, the normal MME 31 sendsthe MTC UE 11 a NAS retransmission request message via the eNB 20 atstep 669.

Otherwise, if it is determined that the UE 10 or 11 is no the MTC UE 11at step 665, the normal MME 31 allocates a GUTI to the UE 10 or 11 atstep 671. The normal MME 31 sends the UE 10 or 11 a NAS response messageat step 673. At this time, the normal MME 31 transmits the NAS responsemessage including the corresponding GUTI. If it is determined that thereis no need to allocate a GUTI to the UE 10 or 11 at step 663, the normalMME 31 sends the UE 10 or 11 the NAS response message via the eNB 20 atstep 675.

FIG. 17 is a flowchart illustrating the operation procedure of the eNB20 of FIG. 15.

Referring to FIG. 17, the eNB 20 establishes an RRC connection with theUE 10 or 11 at step 681. If a NAS request message is received from theUE 10 or 11, the eNB 20 detects this at step 683 and selects an MME 30,31, or 33 at step 685. At this time, if an entity ID is received alongwith the NAS request message, the eNB 20 selects the MME 30, 31, or 33matched with the entity ID. If no entity ID is received, the eNB 20selects an MME 30, 31, or 33 arbitrarily. If an MTC indicator isreceived along with the NAS request message, the eNB 20 selects the MTCMME 33. If no MTC indicator is received, the eNB 20 selects the normalMME 31. The eNB 20 delivers the NAS request message to the MME 30, 31,or 33 at step 687.

Next, if an MME reselection request message is received from the MME 30,31, or 33, the eNB 20 detects this at step 689. Afterward, if a NASretransmission request message is received from the MME 30, 31, or 33,the eNB 20 detects this at step 691 and delivers the NAS retransmissionrequest message to the MTC UE 11 at step 693. If a NAS request isreceived, the eNB 20 detects this at step 695 and reselects an MME 30,31, or 33 at step 697. At this time, the eNB 20 selects the MTC MME 33.Here, if an entity ID is received in the MME reselection requestmessage, the eNB 20 selects the MTC MME 33. Otherwise, if not entity IDis received, the eNB selects the MTC MME 33 arbitrarily. The eNB 20delivers the NAS request message to the reselected entity 30, 31, or 33.If a NAS response message from the MME 30, 31, or 33, the eNB 20 detectsthis at step 701 and delivers the NAS response message to the UE 10 or11 at step 703.

According to the above-described embodiments, it is possible to connectthe MTC UE 11 to the MTC MME 33 efficiently in the wirelesscommunication system. That is, the MTC UE 11 can connect to the MME 33efficiently through cooperation between eNB 20 and normal MME 31 ornormal MME 31 and MTC MME 33.

Although the description is directed to the connection procedure betweenMTC UE 11 and the MTC MME 33 in the wireless communication system, thepresent invention is not limited thereto. That is, the present inventionalso can be implemented by connecting the normal UE to the normal MME 31efficiently through cooperation between the eNB 20 and the normal MME 31or the normal MME 31 and MTC MME 33.

In the wireless communication system, it is possible for connecting theUE 10 or 11 to the MME 30, 31, or 33 corresponding to the supplementaryfunction efficiently. That is, the UE 10 or 11 is capable beingconnected to the MME 30, 31, or 33 efficiently through cooperationbetween the eNB 20 and the MME 30, 31, or 33 or among the MMEs 30, 31,and 33 supporting different supplementary functions.

Although the descriptions have been directed to the case where theconnection between the UE and the MME is established in association witha specific supplementary function, the present invention is not limitedthereto. That is, the present invention can be implemented in such a waythat the connection between the UE and the MME is established accordingto the load status of the MME.

For example, if the eNB request for the identity information of a UE,the MME checks the current load status. At this time, the MME determineswhether the current load is greater than a predetermined thresholdvalue, i.e. whether overload occurs. If it is determined that thecurrent load is not greater than the threshold value, i.e. no overloadoccurs, the MME is capable of allocating the identity information to theUE. Otherwise, if it is determined that the current load is greater thanthe threshold value, i.e. overload occurs, the MME requests another MMEfor the identity information of the UE. That is, if overload occurs, theMME suspends the connection of the UE and request another MME for theidentity information. In this way, the other MME is capable ofallocating identity information to the UE. Here, the MME is capable oftransmitting the identity information to the UE via the other MME.Furthermore, the UE is capable of trying connection to another MME usingthe corresponding identity information.

According to the present invention, it is possible to connect a UE to anMME efficiently in the wireless communication system. That is, the UE iscapable of being connected to an MME efficiently through cooperationbetween the eNB and the MME or among the MMEs. At this time, the MMEs iscapable of cooperating among each other according to the supportablesupplementary function or load status.

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove with specific terminology, this is forthe purpose of describing particular embodiments only and not intendedto be limiting of the invention. While particular embodiments of thepresent invention have been illustrated and described, it would beobvious to those skilled in the art that various other changes andmodifications can be made without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. A connection method of a first mobilitymanagement entity (MME) comprising: identifying a second MME supportinga user equipment (UE) based on received information associated with theUE from a home subscriber server (HSS); transmitting a request messagecomprising non-access stratum (NAS) message to the base station.
 2. Aconnection method of a base station comprising: identifying a secondmobility management entity (MME) supporting a user equipment (UE) basedon received information associated with the terminal from a first MME;transmitting an initial UE message comprising non-access stratum (NAS)request message to the second MME.